Dr. Gass
HCOM 235
COMMON FALLACIES IN REASONING
1. FAULTY CAUSE: (post hoc ergo propter hoc) mistakes correlation or association for
causation, by assuming that because one thing follows another it was caused by the
other.
example: A black cat crossed Babbs' path yesterday and, sure enough, she was
involved in an automobile accident later that same afternoon.
example: The “Bambino curse” claimed that the Boston Red Sox could never win
the world series because they traded Babe Ruth to the Yankees in 1920. After
an 80 year draught, however, the Red Sox finally won a world series in 2004,
thus breaking the curse.
2. SWEEPING GENERALIZATION: (dicto simpliciter) assumes that what is true of the
whole will also be true of the part, or that what is true in most instances will be true in all
instances.
example: Muffin must be rich or have rich parents, because she belongs to ZXQ,
and ZXQ is the richest sorority on campus.
example: I'd like to hire you, but you're an ex-felon and statistics show that 80%
of ex-felons are recidivists.
3. HASTY GENERALIZATION: bases an inference on too small a sample, or on an
unrepresentative sample. Often, a single example or instance is used as the basis for a
broader generalization.
example: Movie stars are really rude. I asked Matthew McConaughey for his
autograph in a restaurant in Westwood the other evening, and he told me to “get
lost.”
example: Pit Bulls are actually gentle, sweet dogs. My next door neighbor has
one and his dog loves to romp and play with all the kids in the neighborhood!
4. FAULTY ANALOGY: (can be literal or figurative) assumes that because two things,
events, or situations are alike in some known respects, that they are alike in other
unknown respects.
example: What's the big deal about the early pioneers killing a few Indians in
order to settle the West? After all, you can't make an omelet without breaking a
few eggs.
example: Banning the sale of “bongs” on the Internet to curb drug use makes
about as much sense as banning bikini sales to reduce promiscuity.
5. APPEAL TO IGNORANCE: (argumentum ad ignorantiam) attempts to use an
opponent's inability to disprove a conclusion as proof of the validity of the conclusion,
i.e. "You can't prove I'm wrong, so I must be right."
example: We can safely conclude that there is intelligent life elsewhere in the
galaxy, because thus far no one has been able to prove that there is not.
example: The new form of experimental gene replacement therapy must be
working. Not a single patient has returned to complain!
6. BIFURCATION: (either-or, black or white, all or nothing fallacy) assumes that two
categories are mutually exclusive and exhaustive, that is, something is either a member
of one or the other, but not both or some third category.
example: Either you favor a strong national defense, or you favor allowing other
nations to dictate our foreign policy.
example: Either you are with the terrorists or you are with the United States.
7. FALSE DILEMMA: (a form of bifurcation) implies that one of two outcomes is
inevitable, and both have negative consequences.
example: Either you buy a large car and watch it guzzle away your paycheck, or
you buy a small car and take a greater risk of being injured or killed in the event
of an accident.
example: You can put your money in a savings account, in which case the IRS
will tax you on the interest, and inflation will erode the value of your money, or
you can buy stocks and watch your 401k fall like a sack of hammers.
8. FAULTY SIGN: (also includes argument from circumstance) wrongly assumes that
one event or phenomenon is a reliable indicator or predictor of another event or
phenomenon.
example: the cars driving in the opposite direction have their lights on; they must
be part of a funeral procession.
example: The Boswell’s must be home. The lights are on upstairs.
9. DAMNING THE SOURCE: (ad hominem, sometimes called the genetic fallacy)
attempts to refute an argument by indicting the source of the argument, rather than the
substance of the argument itself.
example: There is no reason to listen to the arguments of those who oppose
school prayer, for they are the arguments of atheists!
example: Candidate __________ never served in the armed forces and we don’t
want a coward for our Commander in Chief.
10. TU QUOQUE: (look who's talking or two wrongs make a right) pointing to a similar
wrong or error committed by another.
example: Gee, Mom and Dad, how can you tell me not to smoke grass when you
both smoke cigarettes and drink alcohol?
example: The United States has no business criticizing the human rights policies
of Third World nations, not as long as discrimination and segregation continue to
exist in the United States.
11. EQUIVOCATION: allows a key word or term in an argument to shift its meaning
during the course of the argument. The result is that the conclusion of the argument is
not concerned with the same thing as the premise(s).
example: Only man is rational. No woman is a man. Therefore, no woman is
rational.
example: No one who has the slightest acquaintance with science can
reasonably doubt that the miracles in the Bible actually took place. Every year we
witness countless new miracles in the form recombinant DNA, micro-chips, organ
transplants, and the like. (note: the word "miracle" does not have the same
meaning in each case)
12. BEGGING THE QUESTION: (petitio principii) entails making an argument, the
conclusion of which is based on an unstated or unproven assumption. In question form,
this fallacy is known as a COMPLEX QUESTION.
example: Abortion is murder, since killing a baby is an act of murder.
example: Have you stopped beating your wife?
13. TAUTOLOGY: (a sub-category of circular argument) defining terms or qualifying an
argument in such a way that it would be impossible to disprove the argument. Often, the
rationale for the argument is merely a restatement of the conclusion in different words.
example: The Bible is the word of God. We know this because the Bible itself
tells us so.
example: You are a disagreeable person and, if you disagree with me on this, it
will only further prove what a disagreeable person you are.
14. APPEAL TO AUTHORITY: (ipse dixit also called ad verecundiam sometimes)
attempts to justify an argument by citing a highly admired or well-known (but not
necessarily qualified) figure who supports the conclusion being offered.
example: If it's good enough for (insert celebrity's name here), it's good enough
for me.
example: Laws against marijuana are plain silly. Why, Thomas Jefferson is
known to have raised hemp on his own plantation.
15. APPEAL TO TRADITION: (don't rock the boat or ad verecundiam) based on the
principle of "letting sleeping dogs lie". We should continue to do things as they have
been done in the past. We shouldn't challenge time-honored customs or traditions.
example: Of course we have to play "pomp and circumstance" at graduation,
because that's always been the song that is played.
example: Why do I make wine this way? Because my father made wine this way,
and his father made wine this way.
16. APPEAL TO THE CROWD: (ad populum or playing to the gallery) refers to popular
opinion or majority sentiment in order to provide support for a claim. Often the "common
man" or "common sense" provides the basis for the claim.
example: all I can say is that if living together is immoral, then I have plenty of
company.
example: Professor Windplenty's test was extremely unfair. Ask anyone who
took it.
17. STRAW MAN: stating an opponent's argument in an extreme or exaggerated form,
or attacking a weaker, irrelevant portion of an opponent's argument.
example: A mandatory seat belt law could never be enforced. You can't issue
citations to dead people.
example: What woman in her right mind could truly desire total equality with
men? No woman wants the right to be shot at in times of war, the right to have to
pay alimony, or the right to have to develop prostate cancer.
18. SLIPPERY SLOPE: (sometimes called a snowball argument or domino theory)
suggests that if one step or action is taken it will invariably lead to similar steps or
actions, the end results of which are negative or undesirable. A slippery slope always
assumes a chain reaction of cause-effect events which result in some eventual dire
outcome.
example: If the Supreme Court allows abortion, next think you know they'll allow
euthanasia, and it won't be long before society disposes of all those persons
whom it deems unwanted or undesirable.
example: If I let one student interrupt my lecture with a question, then I'll have to
let others and, before long, there won't be any time left for my lecture.
19. APPEALING TO EXTREMES: A fallacy very similar to slippery slope, which
involves taking an argumentative claim or assertion to its extreme, even though the
arguer does not advocate the extreme interpretation. The difference between the two
fallacies is that appealing to extremes does not necessarily involve a sequence of
causal connections.
example: Husband to ex-wife: Well, if you want to be completely fair about
dividing everything up, you should get one of my testicles and I should get one of
your breasts!
example: Debtor to creditor: Hey, you've already repossessed my car and my
television. Why don't you just draw a quart of blood or carve a pound of flesh
from my heart too?
20. HYPOTHESIS CONTRARY TO FACT: This fallacy consists of offering a poorly
supported claim about what might have happened in the past or future if circumstances
or conditions were other than they actually were or are. The fallacy also involves
treating hypothetical situations as if they were fact.
example: If Al Gore had won the 2000 presidential election we wouldn’t have a
global warming problem.
example: If Hitler had not invaded Russia and opened up two military fronts, the
Nazis would surely have won the war.
21. NON SEQUITUR: (literally means "does not follow") in a general sense any
argument which fails to establish a connection between the premises and the
conclusion may be called a non-sequitur. In practice, however, the label non-sequitur
tends to be reserved for arguments in which irrelevant reasons are offered to support a
claim.
example: Both crime victims had tattoos, so the perpetrator must have something
against people with tattoos.
example: Mr Boswell couldn't be the person who poisoned our cat, Truffles,
because when I used to take Truffles for walks he always smiled and said "Hi
neighbor" when we walked by.
22. RED HERRING: attempting to hide a weakness in an argument by drawing attention
away from the real issue. A red herring fallacy is thus a diversionary tactic or an attempt
to confuse or fog the issue being debated. The name of the fallacy comes from the
days of fox hunting, when a herring was dragged across the trail of a fox in order to
throw the dogs off the scent.
example: accused by his wife of cheating at cards, Ned replies "Nothing I do ever
pleases you. I spent all last week repainting the bathroom, and then you said
you didn't like the color."
example: There's too much fuss and concern about saving the environment. We
can't create an Eden on earth. And even if we could, remember Adam and Eve
got bored in the Garden of Eden anyway!
23. APPEAL TO CONSEQUENCES: Cites the desirability or undesirability of the
consequences of an argument as the proof that the argument is good or bad. An arguer
who favors the outcome of an argument might assume the argument is a good one. An
arguer who opposes the outcome of an argument might assume the argument is a bad
one.
example: A student tells a professor, “I know my term paper deserves at least a
‘C’ because if I don’t get a ‘C’ in your class I won’t graduate.”
example: “Using a cell phone can’t pose a health risk, because there is no way I
can function without one.”
24. INCONSISTENCY: advancing an argument that is self-contradictory, or that is
based on mutually inconsistent premises.
example: A used car salespersons says, "Hey, you can’t trust those
other car salesman. They’ll say anything to get you to buy a car
from them."
example: A parent has just read a child the story of Cinderella. The
child asks, "If the coach, and the footmen, and the beautiful clothes
all turned back into the pumpkin, the mice, and the rags, then how
come the glass slipper didn’t change back too?" [the child is
pointing out an inconsistency in the story]